Electronic units are known, such as microcircuit cards, in which a secure element is directly accessible to an external reader via a communication interface, for example conforming to the ISO7816 standard.
In the context of the design of such electronic units, it is advantageous to be able to reuse a secure element used in a preceding application, notably in order to avoid the costs of development and certification of a new type of secure element.
It is moreover increasingly desired to integrate the secure element of such an electronic unit with another sub-system equipping the electronic unit, such as a biometric sensor.
These two objectives are unfortunately often incompatible because the existing secure elements use conventional means of interaction (for example conforming to the ISO7816 standard), which are rarely adapted to an exchange with the aforesaid sub-system (the available biometric sensors being able to use for example serial interfaces of the SPI or I2C type).
Moreover, from the document FR 2 938 094 there is known an electronic unit comprising a communication interface (in this instance of the USB type), a secure element, a sub-system (comprising a memory or a biometric sensor) and a processor (in this instance a microcontroller) connected to the communication interface by means of a first bus, to the secure element by means of a second bus and to the sub-system.
In this document, the processor manages the communication between the communication interface of the USB type and the secure element. This document does not therefore relate to the case where an external reader must be able to access the secure element directly via the communication interface.